Dear list,
I am processing gridded data like DEMs, imported in R from geotiff
files. Of course, such data is regularly gridded, but very often with
NA values. In the framwork of some tests, I have to generate a
neighbourhood of the DEM, so that to extract local extrema of the
layer. For this task, I wrote a function based on the knearneig()
function from the spdep package, with k=4 or k=8, to generate and
analyse the neighbourhood of each point.
Unfortunately, I often have to process big datasets (let's say grids
with between 50,000 and 350,000 points), and that's working but
knearneigh() takes *hours* to process.
Does anybody would have any suggestion to improve the efficiency of this step ?
Thanks,
Pierre